27
Phenomenon
Remedy
Slow startup time
Slow response
PV value fluctuates
Tuning does not end. PV value
fluctuates with a 2
°
C or more
error between SP and PV value.
Tuning does not end. PV value is
stable but PV does not end.
Large overshoot
Control signals repeatedly turn
ON and OFF more than neces-
sary.
Handling Precautions
●
Auto-tuning does not function normally unless the control target is connected.
●
The auto-tuning time from start to finish varies according to the control target.
●
When auto-tuning is executed, control is suspended, and 0 to 100% output is
repeated several times. If this hinders operation, manually set the PID values.
●
Sometimes suitable PID values cannot be obtained according to the control
target. If this happens, manually set the PID values.
The following describes auto-tuning operation:
Operation when the difference between SP and PV values is 10% FS or more and
SP>PV
At startup, operation stabilizes at a tem-
perature of about (SP - PV)/2
↓
The temperature rises again and reaches SP.
↓
Auto-tuning ends when stability is achieved.
Operation when the difference between SP and PV values is 10% FS or less and
SP<PV
Cycling is repeated around the SP value.
↓
Auto-tuning ends when stability is achieved.
Chapter 6 TUNING
Time
SP
Temperature
Execute auto-tuning.
Set
C
T
R
L
to “2”, reset PID
values to factory settings,
and set
C
T
R
L
to “1” to
execute self-tuning.
Reduce the value of time-
proportional cycle (
C
y
C
L
).
Set the value of PV filter (param-
eter item) to “1.0” to “2.0”.
Operation ends though it takes
a long time. The slower the
response of the control target,
the longer tuning takes.
Temperature
Time
SP
2
SP-PV
6-5
Control Troubleshooting
1
2
1
2
5
1
2
1
2
3
4
1
2
4
3
4
1
2
3
4
1
2
5
